Yes, MILKWEED is a Scrabble word!

Letter values in Scrabble US: M 3, I 1, L 1, K 5, W 4, E 1, E 1, D 2.

Is it a valid word?

MILKWEED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any of numerous plants of the genus Asclepias having milky juice and pods that split open releasing seeds with downy tufts
annual Eurasian sow thistle with soft spiny leaves and rayed yellow flower heads

Also: sonchus oleraceus.